JP6919804B2 - Conductive rubber composition, transfer rollers and image forming equipment - Google Patents

Description

The present invention relates to a conductive rubber composition for a transfer roller , a transfer roller including a roller body made of the conductive rubber composition, and an image forming apparatus incorporating the transfer roller.

In an image forming apparatus using an electrophotographic method such as a laser printer, an electrostatic copier, a plain paper facsimile machine, or a combination machine thereof, a toner image formed on a photoconductor is formed on a paper, a plastic film, or the like. A transfer roller is used to transfer to the surface of paper or the like.
The transfer roller contains a cross-linking component for cross-linking the rubber and a foaming agent for foaming the rubber by decomposing it by heating to generate gas, and imparts conductivity. Generally, a roller body made of a sex rubber composition is provided. That is, a roller body is formed by molding the conductive rubber composition into a tubular shape and heating it for cross-linking and foaming to manufacture a transfer roller. Acrylonitrile butadiene rubber (NBR) is the most common rubber that forms the basis of the roller body.

In Patent Document 1, styrene-butadiene rubber (SBR) is used instead of NBR, and the foaming agent is used in combination with a foaming agent that lowers the decomposition temperature of the foaming agent and promotes decomposition. , It is being considered to adjust the blending ratio of the foaming aid.
According to this configuration, since the unit price of SBR is lower than that of NBR, the cost of manufacturing the transfer roller can be reduced. Further, by foaming, the number of materials used can be reduced to further reduce the cost, and the weight of the transfer roller can be reduced to reduce the cost such as transportation cost.

In addition, by adjusting the blending ratio of the foaming agent and the foaming aid within a predetermined range, the roller body is provided with an appropriate degree of flexibility suitable for use as a transfer roller, and the cell of the foaming cell. The diameter can be reduced to improve the smoothness of the outer peripheral surface of the roller body.
That is, when the foaming aid is added, the decomposition temperature of the foaming agent is lowered, so that the foaming agent decomposes and foams almost at the same time in substantially the entire tubular body in a very short time from the start of heating. Then, the foaming agent-derived foam cells that are expanding due to foaming are adjacent to each other, and as a result of suppressing expansion by each other's expansion force, the individual cell diameters become smaller.

Therefore, according to the transfer roller provided with the roller body, it is possible to improve the image quality of the formed image by improving the smoothness of the outer peripheral surface of the roller body while reducing the cost as described above. ..
As the rubber forming the roller body, in Patent Document 1, together with SBR, epichlorohydrin rubber for imparting ionic conductivity to the roller body and ethylene propylene diene rubber (EPDM) for improving the ozone resistance of the roller body. Is used together.

JP-A-2015-34878

In recent years, with the globalization of the image forming apparatus market, the usage environment has been diversified, and the image forming apparatus is required to be able to form a clear image with stable image quality under any usage environment. Is becoming.
However, according to the study of the inventor, the transfer roller to which the ion conductivity is imparted by the ion conductive rubber such as epichlorohydrin rubber has a problem that the roller resistance value fluctuates greatly due to the difference in the usage environment, that is, the difference in temperature and humidity. There is. Then, the roller resistance value of the transfer roller fluctuates greatly due to the difference in the place where the image forming apparatus incorporating the transfer roller is installed, or even in the same place due to changes in climate, weather, etc. May affect the image quality of.

For example, instead of the ionic conductive rubber, a salt having ionic conductivity and having a smaller molecular weight than the crosslinked product of the rubber, such as a salt of an anion having a fluoro group and a sulfonyl group in the molecule (hereinafter, “ion”). It may be abbreviated as "salt") to prepare a conductive rubber composition. According to the inventor's study, when the roller body is formed of such a conductive rubber composition, the fluctuation of the roller resistance value of the transfer roller due to the difference in the usage environment is compared with that of the conductive rubber composition containing the ionic conductive rubber. Can be made smaller.

However, when the transfer roller provided with the roller body made of the conductive rubber composition containing the ionic salt is continuously energized, the roller resistance value of the transfer roller rises significantly compared to the initial value. There is a problem of affecting the image quality of the formed image such as image density. The main reason for this is that the ionic salt moves within the roller body under the influence of an external electric field during continuous energization. That is, as described above, the ionic salt has a smaller molecular weight than the crosslinked product of rubber, and because of its structure, it is easily moved in the roller body under the influence of an external electric field.

Therefore, for example, the ion salts uniformly distributed in the roller body in the initial state move to the vicinity of the outer peripheral surface of the roller body due to continuous energization, or the moved ion salts bloom (precipitate) on the outer peripheral surface. As a result, the abundance ratio of ionic salts in the roller body may decrease or the distribution may vary, and as a result, the roller resistance value of the transfer roller may increase significantly. Moreover, the ionic salt bloomed on the surface contaminates the photoconductor and the like, which also causes deterioration of the image quality of the formed image.

An object of the present invention is to continue to form an image with good image quality because the fluctuation of the roller resistance value due to the difference in the usage environment and the increase of the roller resistance value during continuous energization are small and the roller resistance value is stable. It is an object of the present invention to provide a conductive rubber composition which can form a transfer roller capable of forming a roller body. Another object of the present invention is to provide a transfer roller including a roller body formed by using the conductive rubber composition, and an image forming apparatus incorporating the transfer roller.

The present invention comprises rubber, a cross-linking component for cross-linking the rubber, a foaming component for foaming the rubber , conductive carbon black , and a potassium salt of an anion having a fluoro group and a sulfonyl group in the molecule. The rubber contains at least one selected from the group consisting of styrene butadiene rubber and acrylonitrile butadiene rubber, and epichlorohydrin rubber having an ethylene oxide content of 50 mol% or more and 80 mol% or less, and the compounding ratio of the epichlorohydrin rubber. Is 20 parts by mass or more and 30 parts by mass or less in the total amount of 100 parts by mass of the rubber, and the compounding ratio of the conductive carbon black is 1 part by mass or more and 10 parts by mass or less per 100 parts by mass of the total amount of the rubber. In addition, the mixing ratio of the potassium salt is 0.01 parts by mass or more and 1 part by mass or less per 100 parts by mass of the total amount of the rubber, which is a conductive rubber composition for a transfer roller.

Further, the present invention is an image forming apparatus incorporating the crosslinked conductive rubber composition of the present invention, a transfer roller including a tubular roller body made of a foam, and the transfer roller.

According to the present invention, the fluctuation of the roller resistance value due to the difference in the usage environment and the increase of the roller resistance value during continuous energization are small, and the roller resistance value is stable, so that an image with good image quality can be continuously formed. It is possible to provide a conductive rubber composition that can form a transfer roller that can form a roller body. Further, according to the present invention, it is possible to provide a transfer roller including a roller body formed by using the conductive rubber composition, and an image forming apparatus incorporating the transfer roller.

It is a perspective view which shows the appearance of an example of Embodiment of the transfer roller of this invention. It is a figure explaining the method of measuring the roller resistance value of a transfer roller.

<< Conductive rubber composition >>
The present invention comprises rubber, a cross-linking component for cross-linking the rubber, a foaming component for foaming the rubber , conductive carbon black , and a potassium salt of an anion having a fluoro group and a sulfonyl group in the molecule. The rubber contains at least one selected from the group consisting of styrene butadiene rubber and acrylonitrile butadiene rubber, and epichlorohydrin rubber having an ethylene oxide content of 50 mol% or more and 80 mol% or less, and the compounding ratio of the epichlorohydrin rubber. Is 20 parts by mass or more and 30 parts by mass or less in the total amount of 100 parts by mass of the rubber, and the compounding ratio of the conductive carbon black is 1 part by mass or more and 10 parts by mass or less per 100 parts by mass of the total amount of the rubber. In addition, the mixing ratio of the potassium salt is 0.01 parts by mass or more and 1 part by mass or less per 100 parts by mass of the total amount of the rubber, which is a conductive rubber composition for a transfer roller.

When the roller body is formed using the conductive rubber composition of the present invention, the crosslinked product of epichlorohydrin rubber that does not move in the roller body even under the influence of an external electric field causes substantially uniform ions in the entire roller body. By ensuring conductivity and suppressing an increase in the roller resistance value during continuous energization, and by using a small amount of the above-mentioned potassium salt in combination, fluctuations in the roller resistance value due to differences in the usage environment can be suppressed.

Therefore, according to the conductive rubber composition of the present invention, the fluctuation of the roller resistance value due to the difference in the usage environment and the increase of the roller resistance value at the time of continuous energization are small, and the roller resistance value is stable, so that the image quality is improved. It is possible to form a roller body of a transfer roller that can continue to form a good image.
Further, according to the conductive rubber composition of the present invention, by using the potassium salt and the epichlorohydrin rubber in combination, as described above, the conductive rubber is mixed with both components at a lower ratio than usual. The roller resistance value of the transfer roller provided with the roller body is determined in combination with the fact that the roller body made of the composition is imparted with good ionic conductivity and the conductive carbon black is blended to impart electron conductivity. , Can be set in a range suitable for the transfer roller. Therefore, the manufacturing cost of the transfer roller can be reduced. In particular, when SBR is selected as the rubber to be used in combination with epichlorohydrin rubber, the blending ratio of SBR, which has a high cost merit, can be increased, so that the cost can be further reduced.

<Epichlorohydrin rubber>
As the epichlorohydrin rubber, various polymers containing epichlorohydrin as a repeating unit and having ionic conductivity can be used.
Examples of the epichlorohydrin rubber include epichlorohydrin homopolymer, epichlorohydrin-ethylene oxide binary copolymer (ECO), epichlorohydrin-propylene oxide binary copolymer, epichlorohydrin-allyl glycidyl ether binary copolymer, and epichlorohydrin-ethylene oxide. -Allyl glycidyl ether ternary copolymer (GECO), epichlorohydrin-propylene oxide-allyl glycidyl ether ternary copolymer, epichlorohydrin-ethylene oxide-propylene oxide-allyl glycidyl ether quaternary copolymer, etc. The above can be mentioned.

Above all, in the above-mentioned combination system with potassium salt, a copolymer containing ethylene oxide, particularly ECO and / / Alternatively, GECO is preferable.
However, in the present invention, ethylene oxide content in the both copolymers are both 5 0 mol% or more, it is necessary that 8 0 mol% or less.

Ethylene oxide works to lower the roller resistance value of the transfer roller. However, if the ethylene oxide content is less than this range, such an action cannot be sufficiently obtained, so that the roller resistance value of the transfer roller may not be sufficiently reduced. On the other hand, when the ethylene oxide content exceeds the above range, crystallization of ethylene oxide occurs and the segment movement of the molecular chain is hindered, so that the roller resistance value of the transfer roller tends to increase. In addition, the roller body after cross-linking and foaming becomes too hard to obtain appropriate flexibility suitable for use as a transfer roller, or the viscosity of the conductive rubber composition before cross-linking increases during heating and melting. As a result, the processability and foamability of the conductive rubber composition may decrease.

The epichlorohydrin content in ECO is the remaining amount of ethylene oxide content. Namely, epichlorohydrin content is 20 mol% or more, Ru der 50 mol% or less.
The allyl glycidyl ether content in GECO is preferably 0.5 mol% or more, particularly preferably 2 mol% or more, and preferably 10 mol% or less, particularly 5 mol% or less.

The allyl glycidyl ether itself functions as a side chain to secure a free volume, thereby suppressing the crystallization of ethylene oxide and lowering the roller resistance value of the transfer roller. However, if the allyl glycidyl ether content is less than this range, such an action cannot be sufficiently obtained, so that the roller resistance value of the transfer roller may not be sufficiently reduced. On the other hand, allyl glycidyl ether functions as a cross-linking point at the time of cross-linking of GECO. Therefore, when the allyl glycidyl ether content exceeds the above range, the cross-linking density of GECO becomes too high and the segment movement of the molecular chain is hindered. On the contrary, the roller resistance value of the transfer roller tends to increase.

The epichlorohydrin content in GECO is the remaining amount of ethylene oxide content and allyl glycidyl ether content. That is, the epichlorohydrin content is preferably 10 mol% or more, particularly 19.5 mol% or more, and 49.5 mol% or less, particularly 40 mol% or less.
The GECO is not only a copolymer in a narrow sense obtained by copolymerizing the three types of monomers described above, but also an epichlorohydrin-ethylene oxide binary copolymer (ECO) using allyl glycidyl ether. Denatured variants are also known. In the present invention, any of these GECOs can be used. One or more of these epichlorohydrin rubbers can be used.

<SBR>
As the SBR, various SBRs obtained by copolymerizing styrene and butadiene by various polymerization methods such as an emulsion polymerization method and a solution polymerization method and having crosslinkability can be used.
As the SBR, high styrene type, medium styrene type, and low styrene type SBR classified according to the styrene content can be used.

Further, as the SBR, there are an oil-extending type in which the flexibility is adjusted by adding a spreading oil and a non-oil-extending type in which no spreading oil is added. In the present invention, in order to prevent contamination of the photoconductor, bleeding is performed. It is preferable to use a non-oil-extending type SBR that does not contain spreading oil that can be a substance. One or more of these SBRs can be used.
<NBR>
As the NBR, various NBRs synthesized by copolymerizing acrylonitrile and butadiene by various polymerization methods such as an emulsion polymerization method and having crosslinkability can be used.

The NBR includes low nitrile NBR having an acrylonitrile content of 24% or less, medium nitrile NBR having 25 to 30%, medium and high nitrile NBR having 31 to 35%, and high nitrile NBR having 36 to 42%, and 43% or more. Any ultra-high nitrile NBR can be used.
Further, as the NBR, there are an oil-extended type in which the flexibility is adjusted by adding extendable oil and a non-oil-extended type in which no extensibility oil is added. In the present invention, in order to prevent contamination of the photoconductor, It is preferable to use a non-oil-extending type NBR that does not contain a spreading oil that can be a bleeding substance. One or more of these NBRs can be used.

<Other rubber>
As the rubber, at least one selected from the group consisting of EPDM, chloroprene rubber (CR), and acrylic rubber (ACM) may be used in combination, if necessary. Of these, when EPDM is used in combination, the ozone resistance of the roller body can be improved as described above. Further, when CR and / or ACM, which are polar rubbers, are used in combination, the roller resistance value of the transfer roller can be finely adjusted. In addition, it is possible to form a porous structure that is as uniform as possible without uneven foaming. In terms of this effect, CR is preferable as the polar rubber.

(EPDM)
As the EPDM, various EPDMs in which a double bond is introduced in the main chain can be used by adding a small amount of a third component (diene component) to ethylene and propylene.
As EPDM, various products are provided depending on the type and amount of the third component. Typical third components include, for example, ethylidene norbornene (ENB), 1,4-hexadiene (1,4-HD), dicyclopentadiene (DCP) and the like. As the polymerization catalyst, a Ziegler catalyst is generally used.

Further, as EPDM, there are an oil-extending type in which the flexibility is adjusted by adding spreading oil and a non-oil-extending type in which no spreading oil is added. In the present invention, in order to prevent contamination of the photoconductor, It is preferable to use non-oil-extending type EPDM that does not contain spreading oil that can be a bleeding substance. One or more of these EPDMs can be used.
(CR)
As the CR, various CRs synthesized by emulsion polymerization of chloroprene and having crosslinkability can be used. CR is classified into a sulfur-modified type and a non-sulfur-modified type according to the type of molecular weight modifier used for emulsion polymerization of chloroprene.

Of these, the sulfur-modified type CR is synthesized by plasticizing a polymer obtained by copolymerizing chloroprene and sulfur as a molecular weight modifier with thiuram disulfide or the like to adjust the viscosity to a predetermined value.
Further, the non-sulfur-modified type CR is classified into, for example, a mercaptan-modified type, a xanthate-modified type, and the like.

The mercaptan-modified type CR is synthesized in the same manner as the sulfur-modified type CR except that alkyl mercaptans such as n-dodecyl mercaptan, tert-dodecyl mercaptan, and octyl mercaptan are used as molecular weight modifiers. Further, the xanthate-modified type CR is also synthesized in the same manner as the sulfur-modified type CR except that the alkylxanthate compound is used as a molecular weight modifier.

CRs are classified into slow crystallization rates, moderate crystallization rates, and fast crystallization rates based on their crystallization rates. In the present invention, any type of CR may be used, but among them, a non-sulfur-modified type CR having a slow crystallization rate is preferable.
Further, as CR, a copolymer of chloroprene and another copolymerization component may be used. Examples of such other copolymerization components include 2,3-dichloro-1,3-butadiene, 1-chloro-1,3-butadiene, styrene, acrylonitrile, methacrylic nitrile, isoprene, butadiene, acrylic acid, and acrylic acid ester. , Methacrylic acid, and methacrylic acid ester and the like.

Further, as CR, there are an oil-extending type in which the flexibility is adjusted by adding spreading oil and a non-oil-extending type in which no spreading oil is added. In the present invention, in order to prevent contamination of the photoconductor, It is preferable to use a non-oil-extending type CR that does not contain a spreading oil that can be a bleeding substance. One or more of these CRs can be used.
<Rubber mixing ratio>
As described above, the blending ratio of epichlorohydrin rubber needs to be 20 parts by mass or more and 30 parts by mass or less in the total amount of 100 parts by mass of rubber.

If the blending ratio of the epichlorohydrin rubber is less than this range, the above-mentioned effect of ensuring substantially uniform ionic conductivity in the entire roller body cannot be obtained by blending the epichlorohydrin rubber. Further, in order to adjust the roller resistance value of the transfer roller to a range suitable for the transfer roller, it is necessary to add a large amount of potassium salt in excess of 1 part by mass per 100 parts by mass of the total amount of rubber, and continuous energization is required. Occasionally, the amount of potassium salt that moves within the roller body increases. Therefore, in combination with these factors, the roller resistance value greatly increases during continuous energization. In addition, the effect of reducing the manufacturing cost of the transfer roller by using the epichlorohydrin rubber and the potassium salt in combination becomes insufficient.

On the other hand, when the blending ratio of epichlorohydrin rubber exceeds the above range, the fluctuation of the roller resistance value becomes large due to the difference in the usage environment even if the potassium salt is used in combination. In addition, the effect of reducing the manufacturing cost of the transfer roller by using the epichlorohydrin rubber and the potassium salt in combination becomes insufficient.
On the other hand, by setting the blending ratio of epichlorohydrin rubber in the above range, the fluctuation of the roller resistance value due to the difference in the usage environment and the increase of the roller resistance value during continuous energization are small, and the roller resistance value becomes stable. Therefore, it is possible to form a roller body of a transfer roller that can continue to form an image with good image quality. It is also possible to reduce the manufacturing cost of the transfer roller.

The blending ratio of SBR and / or NBR is the remaining amount of epichlorohydrin rubber when other rubbers such as EPDM are not blended. That is, the blending ratio of SBR and / or NBR is 70 parts by mass or more and 80 parts by mass or less in the total amount of 100 parts by mass of rubber. Such a blending ratio is the blending ratio of the SBR or NBR when SBR alone or NBR alone is used in combination with epichlorohydrin rubber, and is the total blending ratio when SBR and NBR are used in combination.

Further, when the other rubber is blended, the blending ratio is preferably 5 parts by mass or more out of 100 parts by mass of the total amount of rubber in order to obtain the above-mentioned effect by blending the other rubber. It is preferably less than or equal to parts by mass. The blending ratio of SBR and / or NBR may be the remaining amount of epichlorohydrin rubber and other rubbers. That is, the blending ratio of SBR and / or NBR is preferably 40 parts by mass or more, and preferably 75 parts by mass or less in the total amount of 100 parts by mass of rubber.

<Potassium salt>
Examples of the anion having a fluoro group and a sulfonyl group in the molecule constituting the potassium salt include one or two such as fluoroalkyl sulfonic acid ion, bis (fluoroalkyl sulfonyl) imide ion, and tris (fluoroalkyl sulfonyl) methide ion. More than seeds can be mentioned.

Among these, examples of the fluoroalkyl sulfonic acid ion include at least one such as _{CF 3} SO ₃ ⁻ and C ₄ F ₉ SO ₃ ^−.
Examples of bis (fluoroalkylsulfonyl) imide ions include (CF ₃ SO ₂ ) ₂ N ⁻ , (C ₂ F ₅ SO ₂ ) ₂ N ⁻ , and (C ₄ F ₉ SO ₂ ) (CF ₃ SO ₂ ). N ⁻ , (FSO ₂ C ₆ F ₄ ) (CF ₃ SO ₂ ) N ⁻ , (C ₈ F ₁₇ SO ₂ ) (CF ₃ SO ₂ ) N ⁻ , (CF ₃ CH ₂ OSO ₂ ) ₂ N ⁻ , ( CF ₃ CF ₂ CH ₂ OSO ₂ ) ₂ N ⁻ , (HCF ₂ CF ₂ CH ₂ OSO ₂ ) ₂ N ⁻ , [(CF ₃ ) ₂ CHOSO ₂ ] ₂ N ^−, etc. ..

Further, examples of the tris (fluoroalkylsulfonyl) methide ion include at least one such as _{(CF 3} SO ₂ ) ₃ C ⁻ and (CF ₃ CH ₂ OSO ₂ ) ₃ C ^−.
As the ion salt, the above-mentioned anionic lithium salt, sodium salt and the like are also widely used. However, since lithium salts and sodium salts have high hygroscopicity and deliquescent properties, they are likely to deliquesce in a high temperature and high humidity environment and bloom on the outer peripheral surface of the transfer roller, for example. When the deliquescent ion salt blooms, the abundance ratio of the ion salt in the roller body decreases or the distribution becomes uneven, so that the roller resistance value of the transfer roller greatly increases, or the ions bloomed on the surface. The salt contaminates the photoconductor and the like, which deteriorates the image quality of the formed image.

On the other hand, since the potassium salt of the anion has low hygroscopicity and deliquescent property, it does not deliquesce even in a high temperature and high humidity environment and does not bloom on the outer peripheral surface of the transfer roller, and the roller resistance of the transfer roller. There is no risk of significantly increasing the value or contaminating the photoconductor and degrading the image quality of the formed image.
In addition, since potassium salt does not cause mass change or deliquescent during measurement due to moisture absorption, it is possible to measure the amount relatively easily and accurately, and the amount of moisture absorption of the semi-conductive rubber composition varies from batch to batch. It also has the advantage of being easy to handle, such as being less likely to occur.

_{As the potassium salt, (CF 3} SO ₂ ) ₂ NK [potassium / bis] is used in terms of such an effect or an effect of improving the ionic conductivity of the conductive rubber composition and lowering the roller resistance value of the transfer roller. (Trifluoromethanesulfonyl) imide] is preferred.
As described above, the mixing ratio of the potassium salt needs to be 0.01 part by mass or more and 1 part by mass or less per 100 parts by mass of the total amount of rubber.

If the mixing ratio of the potassium salt is less than this range, the effect of suppressing the fluctuation of the roller resistance value due to the difference in the usage environment cannot be obtained by using the potassium salt in combination with epichlorohydrin rubber. Therefore, in order to adjust the roller resistance value of the transfer roller to a range suitable for the transfer roller, it is necessary to add a large amount of epichlorohydrin rubber in excess of 30 parts by mass out of 100 parts by mass of the total amount of rubber. Coupled with this, the above fluctuation becomes large. In addition, the effect of reducing the manufacturing cost of the transfer roller by using the epichlorohydrin rubber and the potassium salt in combination becomes insufficient.

On the other hand, when the mixing ratio of the potassium salt exceeds the above range, in order to adjust the roller resistance value of the transfer roller to a range suitable for the transfer roller, the mixing ratio of epichlorohydrin rubber is adjusted to 100 total amount of rubber. It must be less than 20 parts by mass in the mass part, and the effect of ensuring substantially uniform ionic conductivity in the entire roller body as described above cannot be obtained by blending the epichlorohydrin rubber. Therefore, coupled with the increase in the amount of potassium salt that moves in the roller body, the roller resistance value greatly increases during continuous energization. In addition, the effect of reducing the manufacturing cost of the transfer roller by using the epichlorohydrin rubber and the potassium salt in combination becomes insufficient.

On the other hand, by setting the mixing ratio of the potassium salt in the above range, the fluctuation of the roller resistance value due to the difference in the usage environment and the increase of the roller resistance value during continuous energization are small, and the roller resistance value becomes stable. Therefore, it is possible to form a roller body of a transfer roller that can continue to form an image with good image quality. It is also possible to reduce the manufacturing cost of the transfer roller.
<Crosslink component>
Examples of the cross-linking component for cross-linking the rubber include a cross-linking agent and a cross-linking accelerator.

(Crosslinking agent)
Examples of the cross-linking agent include one or more kinds of cross-linking agents such as sulfur-based cross-linking agents, thiourea-based cross-linking agents, triazine derivative-based cross-linking agents, peroxide cross-linking agents, and various monomers. In particular, a sulfur-based cross-linking agent is preferable.
Examples of the sulfur-based cross-linking agent include sulfur such as powdered sulfur, oil-treated powdered sulfur, precipitated sulfur, colloidal sulfur, and dispersible sulfur, and organic sulfur-containing compounds such as tetramethylthium disulfide and N, N-dithiobismorpholine. Etc., and sulfur is particularly preferable.

The mixing ratio of sulfur is such that the rubber is crosslinked well, and a transfer roller having an appropriate flexibility suitable for use as a transfer roller and having a roller body having a small compression set is produced with high productivity. Considering this, the total amount of rubber is preferably 0.5 parts by mass or more per 100 parts by mass, and preferably 2 parts by mass or less.
When, for example, oil-treated powdered sulfur, dispersible sulfur, or the like is used as sulfur, the above-mentioned compounding ratio is the ratio of sulfur itself as an active ingredient contained therein.

When an organic sulfur-containing compound is used as the cross-linking agent, the blending ratio thereof is preferably adjusted so that the ratio of sulfur contained in the molecule per 100 parts by mass of the total amount of rubber is within the above range. ..
(Crosslink accelerator)
Examples of the cross-linking accelerator to be combined with the sulfur-based cross-linking agent include one or more kinds of inorganic accelerators such as slaked lime, magnesia (MgO) and litharge (PbO), and organic accelerators. In addition, examples of the organic accelerator include one or more types such as a thiazole-based accelerator, a thiuram-based accelerator, a sulfenamide-based accelerator, and a dithiocarbamate-based accelerator. Above all, it is preferable to use a thiazole-based accelerator and a thiuram-based accelerator in combination.

Examples of the thiazole-based accelerator include 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, zinc salt of 2-mercaptobenzothiazole, cyclohexylamine salt of 2-mercaptobenzothiazole, 2- (N, N). One or more of -diethylthiocarbamoylthio) benzothiazole, 2- (4'-morpholinodithio) benzothiazole and the like can be mentioned. In particular, di-2-benzothiazolyl disulfide is preferable.

Further, as the thiuram-based accelerator, for example, one kind such as tetramethylthiuram monosulfide, tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, tetrakis (2-ethylhexyl) thiuram disulfide, dipentamethylene thiuram tetrasulfide and the like. Alternatively, two or more types can be mentioned. In particular, tetramethylthiuram monosulfide is preferable.

Considering that the effect of promoting the cross-linking reaction is sufficiently exhibited in the combined system of the above two types of cross-linking accelerators, the blending ratio of the thiazole-based accelerator is 0.5 parts by mass or more per 100 parts by mass of the total amount of rubber. It is preferably 2 parts by mass or less. The blending ratio of the thiuram-based accelerator is preferably 0.5 parts by mass or more and 2 parts by mass or less per 100 parts by mass of the total amount of rubber.
<Foam component>
As the foaming component, a foaming agent that decomposes by heating to generate gas is used.

(Foaming agent)
As the foaming agent, various compounds that decompose by heating to generate gas can be used. Examples of the foaming agent include one or more of 4,4'-oxybis (benzenesulfonyl hydrazide) (OBSH), azodicarbonamide (ADCA), N, N-dinitrosopentamethylenetetramine (DPT) and the like. Can be mentioned. In particular, OBSH is preferable.

The blending ratio of the foaming agent such as OBSH is preferably 1 part by mass or more per 100 parts by mass of the total amount of rubber, and preferably 4 parts by mass or less. If the blending ratio of the foaming agent is less than this range, the distance between the foaming agent particles in the conductive rubber composition becomes large, and adjacent foaming cells originating from the individual foaming agent particles expand each other. The effect of suppressing expansion by force is not sufficiently obtained. Therefore, the cell diameter of the foam cell becomes large as a whole, the smoothness of the outer peripheral surface of the roller body deteriorates, and the effect of improving the image quality of the formed image may not be obtained.

Further, since the conductive rubber composition cannot be sufficiently foamed, the roller body after cross-linking and foaming becomes too hard, and there is a possibility that appropriate flexibility suitable for use as a transfer roller cannot be obtained. Insufficient foaming also has the effect of reducing the amount of material used to reduce the manufacturing cost of the transfer roller and the effect of reducing the weight of the transfer roller to reduce costs such as transportation costs, as described above. May be insufficient.

On the other hand, when the blending ratio of the foaming agent exceeds the above range, the above-mentioned effect of adjacent foam cells expanding due to foaming to suppress expansion due to mutual expansion force becomes excessively strong. The diameter of each cell becomes too small, and the roller body after cross-linking and foaming becomes rather hard, and there is a possibility that appropriate flexibility suitable for use as a transfer roller cannot be obtained.

On the other hand, by setting the blending ratio of the foaming agent within the above range, the diameter of the foaming cell can be appropriately reduced while ensuring good flexibility of the roller body and various advantages of foaming. be able to.
As the foaming component, the foaming agent alone may be used alone, or a foaming aid may be used in combination with the foaming agent.

(Effervescent aid)
As the foaming aid, various compounds that have a function of lowering the decomposition temperature of the foaming agent to be combined and promoting the decomposition of the foaming agent can be used. Examples of the foaming auxiliary agent, for example, if the foaming agent is OBSH and ADCA, urea _{(H 2} NCONH 2) based blowing aid is preferred.

The blending ratio of the foaming aid is preferably 2.5 parts by mass or less per 100 parts by mass of the total amount of rubber. The lower limit of the blending ratio of the foaming aid is 0 parts by mass.
<Conductive carbon black>
By blending conductive carbon black, as described above, electronic conductivity is imparted to the roller body. As the conductive carbon black, for example, HAF is preferable. Since HAF can be uniformly dispersed in the conductive rubber composition, it is possible to impart as uniform electron conductivity as possible to the transfer roller. The blending ratio of the conductive carbon black needs to be 1 part by mass or more and 10 parts by mass or less per 100 parts by mass of the total amount of rubber.
<others>
Various additives may be further added to the conductive rubber composition, if necessary. Examples of the additive include a cross-linking accelerator, an acid receiver, a filler, a plasticizer, a processing aid, a deterioration inhibitor and the like.

Among these, the cross-linking promoting aid includes, for example, a metal compound such as zinc oxide (zinc oxide); fatty acids such as stearic acid, oleic acid, and cottonseed fatty acid, and one or more of conventionally known cross-linking promoting aids. Can be mentioned. The mixing ratio of the cross-linking accelerator is preferably 0.1 part by mass or more, and preferably 7 parts by mass or less per 100 parts by mass of the total amount of rubber.
The antacid functions to prevent the chlorine-based gas generated from the epichlorohydrin rubber and CR during cross-linking from remaining in the roller body, thereby inhibiting cross-linking and contaminating the photoconductor. As the acid receiving agent, various substances that act as acid receptors can be used, and among them, hydrotalcites or magsalats having excellent dispersibility are preferable, and hydrotalcites are particularly preferable.

Further, when hydrotalcites and the like are used in combination with magnesium oxide and potassium oxide, a higher acid receiving effect can be obtained, and contamination of the photoconductor can be prevented more reliably. The blending ratio of the acid receiving agent is preferably 0.1 part by mass or more, and preferably 7 parts by mass or less per 100 parts by mass of the total amount of rubber.
Examples of the filler include one or more of zinc oxide, silica, carbon black, clay, talc, calcium carbonate, magnesium carbonate, aluminum hydroxide and the like. By blending the filler, the mechanical strength of the transfer roller and the like can be improved.

Examples of the plasticizer include various plasticizers such as dibutyl phthalate, dioctyl phthalate, and tricresyl phosphate, and various waxes such as polar wax. Examples of the processing aid include fatty acid metal salts such as zinc stearate. The blending ratio of the plasticizer and / or the processing aid is preferably 3 parts by mass or less per 100 parts by mass of the total amount of rubber.

Examples of the deterioration inhibitor include various antioxidants and antioxidants. Of these, the anti-aging agent works to reduce the environmental dependence of the roller resistance value of the transfer roller and to suppress an increase in the roller resistance value during continuous energization. Examples of the antiaging agent include nickel diethyldithiocarbamate, nickel dibutyldithiocarbamate and the like. The compounding ratio of the antiaging agent is preferably 0.1 part by mass or more and preferably 1 part by mass or less per 100 parts by mass of the total amount of rubber.

Further, as the additive, various additives such as a scorch inhibitor, a lubricant, a pigment, an antistatic agent, a flame retardant, a neutralizing agent, a nucleating agent, and a co-crosslinking agent may be further blended in an arbitrary ratio. good.
《Transfer roller》
FIG. 1 is a perspective view showing an example of an embodiment of the transfer roller of the present invention.
With reference to FIG. 1, the transfer roller 1 of this example is porous and has a single-layered tubular shape due to cross-linking and foam (cross-linked and foam) of a conductive rubber composition containing each of the above components. It is provided with a roller body 2 formed in. The shaft 4 is inserted and fixed in the through hole 3 at the center of the roller body 2.

The shaft 4 is integrally formed of, for example, a metal such as aluminum, an aluminum alloy, or stainless steel.
The shaft 4 is electrically bonded to and mechanically fixed to the roller body 2 via, for example, a conductive adhesive, or a shaft 4 having an outer diameter larger than the inner diameter of the through hole 3 is passed through. By press-fitting into the hole 3, it is electrically joined to the roller body 2 and mechanically fixed. Alternatively, both of them may be used in combination to electrically join the shaft 4 to the roller body 2 and mechanically fix the shaft 4.

To manufacture the transfer roller 1, first, the prepared conductive rubber composition is extruded into a tubular shape using an extruder, then cut to a predetermined length and pressed in a vulcanization can. Heat to crosslink the rubber and foam it.
Next, the crosslinked and foamed tubular body is secondarily crosslinked by heating using an oven or the like, cooled, and then the outer peripheral surface 5 of the roller body 2 is polished so as to have a predetermined outer diameter.

As the polishing method, various polishing methods such as dry traverse polishing can be adopted.
The shaft 4 can be inserted into the through hole 3 and fixed at any time from after the tubular body is cut to after polishing.
However, after cutting, it is preferable to first perform secondary cross-linking and polishing with the shaft 4 inserted through the through hole 3. As a result, warpage and deformation of the roller body 2 due to expansion and contraction during secondary cross-linking can be suppressed. Further, by polishing while rotating around the shaft 4, the workability of the polishing can be improved and the deflection of the outer peripheral surface 5 can be suppressed.

As described above, the shaft 4 is press-fitted into the through hole 3 having an outer diameter larger than the inner diameter of the through hole 3, or is placed before the secondary cross-linking via a conductive thermosetting adhesive. It may be inserted into the through hole 3 of the tubular body of the above.
In the former case, the electrical joining and mechanical fixing with the roller body 2 are completed at the same time as the press-fitting of the shaft 4.

In the latter case, the tubular body is secondarily crosslinked by heating in the oven, and at the same time, the thermosetting adhesive is cured, and the shaft 4 is electrically bonded to the roller body 2. It is fixed mechanically.
Further, as described above, both of them may be used in combination to electrically join the shaft 4 to the roller body and mechanically fix the shaft 4.

In the embodiment of FIG. 1, the roller body 2 has a single-layer structure composed of crosslinked and foamed material of a specific rubber composition containing each of the above-mentioned components, but the roller body has a laminated structure of two or more layers. May be. In that case, the outermost layer constituting the outer peripheral surface may be formed by cross-linking or foaming a specific rubber composition containing each of the above-mentioned components.
《Roller resistance value》
<Variation of roller resistance due to differences in usage environment>
FIG. 2 is a diagram illustrating a method of measuring the roller resistance value of the transfer roller.

With reference to FIGS. 1 and 2, in the present invention, the fluctuation of the roller resistance value of the transfer roller 1 due to the difference in the usage environment is evaluated based on the roller resistance value measured by the following method.
That is, an aluminum drum 6 capable of rotating at a constant rotation speed is prepared, and the outer peripheral surface of the roller body 2 of the transfer roller 1 for measuring the roller resistance value from above on the outer peripheral surface 7 of the aluminum drum 6. 5 is brought into contact.

Further, a DC power supply 8 and a resistor 9 are connected in series between the shaft 4 of the transfer roller 1 and the aluminum drum 6 to form the measurement circuit 10. The DC power supply 8 connects the (−) side to the shaft 4 and the (+) side to the resistor 9. The resistance value r of the resistor 9 is adjusted in the range of 100Ω to 10kΩ so that the significant figure of the measured value of the roller resistance value becomes as large as possible according to the level of the roller resistance value.

Next, a load F of 500 g is applied to both ends of the shaft 4, and the aluminum drum 6 is rotated (rotation speed: 30 rpm) with the roller body 2 pressed against the aluminum drum 6, and direct current is applied between the two. Thirty seconds after applying the applied voltage E of DC 2000V from the power supply 8, the detection voltage V applied to the resistor 9 is measured.
From the measured detection voltage V and the applied voltage E (= 2000V), the roller resistance value R of the transfer roller 1 is basically the equation (i'):
R = r × E / V-r (i ′)
Demanded by. However, since the term of −r in equation (i ′) can be regarded as minute, in the present invention, equation (i):
R = r × E / V (i)
The roller resistance value of the transfer roller 1 is set to the value obtained by.

The roller resistance value R is measured in a low-temperature and low-humidity environment with a temperature of 10 ° C. and a relative humidity of 20%, and in a high-temperature and high-humidity environment with a temperature of 30 ° C. and a relative humidity of 80%. The resistance value R _LL (Ω) and the roller resistance value R _HH (Ω) in a high temperature and high humidity environment are obtained.
Then, seeking difference _logR LL _{-logR HH} between the logarithmic value logR _LL and logR _HH both roller resistance value, the difference fluctuates small ones less than 1.4 (○), change those less than 1.4 Evaluate as large (x).

As is clear from the results of Examples described later, the transfer roller 1 of the present invention can be evaluated as having a difference of 1.8 or less and a small fluctuation in roller resistance value due to a difference in usage environment. can.
<Increase in roller resistance during continuous energization>
With reference to FIGS. 1 and 2 again, a load F of 500 g is applied to both ends of the shaft 4 under a temperature of 23 ° C., a room temperature of 55% relative humidity, and a normal humidity environment, and the roller body 2 is pressed against the aluminum drum 6. In this state, the applied voltage E of DC 2000V is continuously applied from the DC power supply 8 between the two. During this continuous energization, the aluminum drum 6 stops rotating, and the same portion of the roller body 2 is always kept in contact with the aluminum drum 6. The resistance value r of the resistor 9 is adjusted in the range of 100Ω to 10kΩ so that the significant figure of the measured value of the roller resistance value becomes as large as possible according to the level of the roller resistance value.

Next, the transition of the detected voltage V applied to the resistance 9 is recorded immediately after the start of energization, and the roller resistance value R ₀ (Ω) at the start of energization and the roller resistance value R ₃₀ (30 minutes after the start of energization) are recorded. Ω) and.
Then, the ratio R ₃₀ / R ₀ of both roller resistance values is obtained as the increase ratio of the roller resistance values, and the increase ratio of less than 1.5 is small (○), and the increase ratio of 1.5 or more is increased. Evaluate as large (x).

As is clear from the results of Examples described later, the transfer roller 1 of the present invention can be evaluated as having such an increase ratio of 2 or less and a small increase in roller resistance value during continuous energization.
<< Image forming device >>
The image forming apparatus of the present invention is characterized by incorporating the transfer roller of the present invention. Examples of the image forming apparatus of the present invention include various image forming apparatus using an electrophotographic method, such as a laser printer, an electrostatic copier, a plain paper facsimile apparatus, or a multifunction device thereof.

Hereinafter, the present invention will be further described based on Examples and Comparative Examples, but the configuration of the present invention is not necessarily limited to these.
<Example 1>
As rubber, 20 parts by mass of GECO [HYDRIN (registered trademark) T3108 manufactured by Nippon Zeon Corporation] and NBR [JSR N250 SL manufactured by JSR Corporation, non-oil-extended, low nitrile NBR, acrylonitrile content: 20% ] 80 parts by mass was used in combination.

Then, 100 parts by mass of the total amount of both rubbers was kneaded by mixing the following components while kneading with a Bambali mixer.

Each component in Table 1 is as follows. The mass part in the table is a mass part per 100 parts by mass of the total amount of rubber.
Conductive carbon black : Carbon black HAF [Seast 3 manufactured by Tokai Carbon Co., Ltd.]
Foaming agent: OBSH [Neocerbon (registered trademark) N # 1000S manufactured by Eiwa Kasei Kogyo Co., Ltd.]
Potassium salt: Potassium bis (trifluoromethanesulfonyl) imide [EF-N112 manufactured by Mitsubishi Material Denshikase Co., Ltd.]
Crosslinking accelerator I: Stearic acid [Tsubaki manufactured by NOF CORPORATION]
Crosslink Accelerator II: Zinc Oxide 2 [Mitsui Mining & Smelting Co., Ltd.]
Antacid: Hydrotalcites [DHT-4A (registered trademark) -2 manufactured by Kyowa Chemical Industry Co., Ltd.]
Then, while continuing the kneading, the following cross-linking components were blended and further kneaded to prepare a conductive rubber composition.

Each component in Table 2 is as follows. The mass part in the table is a mass part per 100 parts by mass of the total amount of rubber.
Sulfur-based cross-linking agent: powdered sulfur [manufactured by Tsurumi Chemical Industry Co., Ltd.]
Crosslinking accelerator DM: Di-2-benzothiazolyl disulfide [SUNSINE MBTS manufactured by Shandong Shanxian Chemical Co., Ltd., thiazole-based accelerator]
Crosslinking accelerator TS: Tetramethylthiuram monosulfide [Sunceller (registered trademark) TS manufactured by Sanshin Chemical Industry Co., Ltd., thiuram-based accelerator]
(Transfer roller)
The prepared conductive rubber composition is supplied to an extrusion molding machine, extruded into a tubular shape having an outer diameter of φ20 mm and an inner diameter of φ8.5 mm, cut to a predetermined length, and used for cross-linking with an outer diameter of φ2.2 mm. It was attached to the temporary shaft of.

Then, in the vulcanization can, pressure and heating are performed by pressurizing steam for 135 ° C. × 10 minutes and then 160 ° C. × 20 minutes to foam the tubular body with the gas generated by the decomposition of the foaming agent and rubber. Was crosslinked.
Next, this tubular body is reattached to a shaft having an outer diameter of φ12 mm coated with a conductive thermosetting adhesive on the outer peripheral surface, and heated in an oven at 160 ° C. for 60 minutes for secondary cross-linking. The thermosetting adhesive was cured, electrically bonded to the shaft, and mechanically fixed.

Then, after shaping both ends of the tubular body, the outer peripheral surface is traverse-ground using a cylindrical grinding machine to finish the outer diameter to φ24 mm (tolerance ± 0.1 mm) to form a roller body and transfer. Manufactured rollers.
<Example 2>
A conductive rubber composition was prepared in the same manner as in Example 1 except that the blending ratio of the foaming agent was 2.5 parts by mass per 100 parts by mass of the total amount of rubber, and a transfer roller was manufactured.

<Example 3>
The amount of GECO is 30 parts by mass, the amount of NBR is 70 parts by mass, the mixing ratio of potassium salt is 0.5 parts by mass, and the mixing ratio of foaming agent is 2.5 parts by mass per 100 parts by mass of total rubber. A conductive rubber composition was prepared in the same manner as in Example 1 except that the parts were used, and a transfer roller was manufactured.

<Comparative example 1>
A conductive rubber composition was prepared and a transfer roller was produced in the same manner as in Example 1 except that the amount of GECO was 30 parts by mass, the amount of NBR was 70 parts by mass, and no potassium salt was added. ..
<Comparative example 2>
The conductive rubber composition was the same as in Example 1 except that GECO was not blended with the amount of NBR set to 100 parts by mass and the mixing ratio of potassium salt was set to 3 parts by mass per 100 parts by mass of the total amount of rubber. A product was prepared and a transfer roller was manufactured.

<Comparative example 3>
The conductive rubber composition is the same as in Example 1 except that the mixing ratio of the potassium salt is 1.5 parts by mass and the mixing ratio of the foaming agent is 2.5 parts by mass per 100 parts by mass of the total amount of rubber. Was prepared to produce a transfer roller.
<Comparative Example 4>
The amount of GECO was 30 parts by mass, the amount of NBR was 70 parts by mass, the blending ratio of the foaming agent was 0.8 parts by mass per 100 parts by mass of the total amount of rubber, and no potassium salt was blended. A conductive rubber composition was prepared in the same manner as in Example 1 except for the above, and a transfer roller was produced.

<Variation of roller resistance due to differences in usage environment>
The fluctuation of the roller resistance value (environmental fluctuation) due to the difference in the usage environment of the transfer rollers manufactured in each Example and Comparative Example was evaluated by the method described above.
<Increase in roller resistance during continuous energization>
The increase in roller resistance (increased energization) of the transfer rollers manufactured in each of the Examples and Comparative Examples during continuous energization was evaluated by the method described above.

The above results are shown in Table 3.

From the results of Examples 1 to 3 and Comparative Examples 1 to 4 in Table 3, in the combined system of epichlorohydrin rubber having a predetermined ethylene oxide content and NBR, the blending ratio of epichlorohydrin rubber was determined in 100 parts by mass of the total amount of rubber. 20 parts by mass or more and 30 parts by mass or less, and potassium salt is 0.01 part by mass or more and 1 part by mass or less per 100 parts by mass of total rubber, and conductive carbon black is 1 mass by mass per 100 parts by mass of rubber. When used in the range of 10 parts or more by mass or more, the fluctuation of the roller resistance value due to the difference in the usage environment and the increase of the roller resistance value during continuous energization are small, and the roller resistance value is stable. It was found that a transfer roller capable of continuing to form a good image of the above can be formed.

<Example 4>
A conductive rubber composition was prepared and a transfer roller was manufactured in the same manner as in Example 1 except that the same amount of SBR [SBR1502 manufactured by Sumitomo Chemical Co., Ltd., non-oil spread] was blended in place of NBR. bottom.
<Example 5>
A conductive rubber composition was prepared in the same manner as in Example 4 except that the blending ratio of the foaming agent was 2.5 parts by mass per 100 parts by mass of the total amount of rubber, and a transfer roller was manufactured.

<Example 6>
The amount of GECO is 30 parts by mass, the amount of SBR is 70 parts by mass, the mixing ratio of potassium salt is 0.5 parts by mass, and the mixing ratio of foaming agent is 2.5 parts by mass per 100 parts by mass of total rubber. A conductive rubber composition was prepared in the same manner as in Example 4 except that the parts were used, and a transfer roller was manufactured.

<Comparative Example 5>
A conductive rubber composition was prepared and a transfer roller was produced in the same manner as in Example 4 except that the amount of GECO was 30 parts by mass, the amount of SBR was 70 parts by mass, and no potassium salt was added. ..
<Comparative Example 6>
The conductive rubber composition was the same as in Example 4 except that GECO was not blended with the amount of SBR being 100 parts by mass and the mixing ratio of potassium salt was 3 parts by mass with respect to the total amount of rubber of 100 parts by mass. A product was prepared and a transfer roller was manufactured.

<Comparative Example 7>
The conductive rubber composition is the same as in Example 4 except that the mixing ratio of the potassium salt is 1.5 parts by mass and the mixing ratio of the foaming agent is 2.5 parts by mass per 100 parts by mass of the total amount of rubber. Was prepared to produce a transfer roller.
<Comparative Example 8>
The amount of GECO was 30 parts by mass, the amount of SBR was 70 parts by mass, the blending ratio of the foaming agent was 0.8 parts by mass per 100 parts by mass of the total amount of rubber, and no potassium salt was blended. A conductive rubber composition was prepared in the same manner as in Example 4 except for the above, and a transfer roller was produced.

For the transfer rollers 1 manufactured in each of the above Examples and Comparative Examples, the fluctuation of the roller resistance value (environmental fluctuation) due to the difference in the usage environment described above and the increase of the roller resistance value during continuous energization (energization increase) were evaluated. The results are shown in Table 4.

From the results of Examples 4 to 6 and Comparative Examples 5 to 8 in Table 4, it was found that the same results as the above-mentioned combination system of epichlorohydrin rubber and NBR can be obtained in the combined system of epichlorohydrin rubber and SBR. That is, the blending ratio of epichlorohydrin rubber having a predetermined ethylene oxide content is 20 parts by mass or more and 30 parts by mass or less in 100 parts by mass of the total amount of rubber, and the potassium salt is 0.01 per 100 parts by mass of the total amount of rubber. By using conductive carbon black of 1 part by mass or more and 1 part by mass or less and conductive carbon black in the range of 1 part by mass or more and 10 parts by mass or less per 100 parts by mass of the total amount of rubber, the roller resistance value may fluctuate due to the difference in the usage environment. It was found that since the increase in the roller resistance value during continuous energization is small and the roller resistance value is stable, a transfer roller capable of continuously forming an image with good image quality can be formed.

In addition, as a result of comparing Examples 1 to 6, it was confirmed that the combined use of epichlorohydrin rubber and SBR having a high cost merit enables further cost reduction as compared with the combined system with NBR. Was done.

F Load V Detection voltage 1 Transfer roller 2 Roller body 3 Through hole 4 Shaft 5 Outer surface 6 Aluminum drum 7 Outer surface 8 DC power supply 9 Resistance 10 Measuring circuit

Claims (5)

The rubber comprises a rubber, a cross-linking component for cross-linking the rubber, a foaming component for foaming the rubber , conductive carbon black , and a potassium salt of an anion having a fluoro group and a sulfonyl group in the molecule. At least one selected from the group consisting of styrene butadiene rubber and acrylonitrile butadiene rubber and epichlorohydrin rubber having an ethylene oxide content of 50 mol% or more and 80 mol% or less are contained, and the blending ratio of the epichlorohydrin rubber is the rubber. 20 parts by mass or more and 30 parts by mass or less in the total amount of 100 parts by mass of the rubber, and the compounding ratio of the conductive carbon black is 1 part by mass or more and 10 parts by mass or less per 100 parts by mass of the total amount of the rubber , and the potassium. A conductive rubber composition for a transfer roller in which the mixing ratio of the salt is 0.01 part by mass or more and 1 part by mass or less per 100 parts by mass of the total amount of the rubber. The foaming component contains 4,4'-oxybis (benzenesulfonyl hydrazide), and the blending ratio of the 4,4'-oxybis (benzenesulfonyl hydrazide) is 1 part by mass or more per 100 parts by mass of the total amount of the rubber. The conductive rubber composition for a transfer roller according to claim 1, which is not more than parts by mass. The conductive rubber composition for a transfer roller according to claim 1 or 2, wherein the rubber further contains at least one selected from the group consisting of ethylene propylene diene rubber, chloroprene rubber, and acrylic rubber. A transfer roller including a cylindrical roller body made of a crosslinked conductive rubber composition for the transfer roller according to any one of claims 1 to 3 and a foam. An image forming apparatus incorporating the transfer roller according to claim 4.

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